Long-term ozone exposure and COPD assessment test (CAT) score: findings from the China Pulmonary Health Study

<bold>Background:</bold> Despite understanding on the impairment effect of ozone on lung function, the association between ozone exposure and chronic respiratory symptoms remains unknown. This study aims to explore the association between long-term ozone exposure and the chronic obstructive pulmonary diseases (COPD) Assessment Test (CAT) score. <bold>Methods:</bold> We extracted individuals with CAT score from the China Pulmonary Health study and used both multivariable linear (CAT score after logarithm transformation as outcome variable) and logistic regression (CAT score > 10 (mild to severe impact) as cutoff) models to explore the association between long-term ozone exposure and CAT score, adjusting for demographic factors, individual risk factors such as smoking and biomass fuel use, survey season, lung function indicators, and longitudinal trends. <bold>Results:</bold> We included 14275 participants (male: 7499 (52.5%)) with mean age of 55.2 ± 12.5 years. The median CAT score was 3.0 (interquartile range (IQR): 0.0-7.0) and the median lag 1-year O3 exposure was 101 μg/m3 (IQR: 95.4-110.0). Per 10 μg/m3 increase in long-term ozone exposure was significantly associated with a 6.2 (95% confidence interval (CI): 3.0-9.4) percent change in CAT score, and an increased risk of having CAT score > 10 (Odds ratio: 1.1, 95% CI: 0.95-1.2). The association was robust after adjusting for PM2.5 concentration. <bold>Discussion:</bold> This study quantified the association between long-term exposure of ozone, and the severity and impact of respiratory symptoms, and such association was independent of PMz.s. It provided further evidence on the magnitude and mechanism of the detrimental effect of ozone on the respiratory system.